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Date: Wed, 07 Aug 2013 16:33:03 +0800
From: David Xu <davidxu@freebsd.org>
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To: dave@mischler.com
Subject: Re: unexpected idprio 31 behavior on 9.2-BETA2 and 9.2-RC1
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On 2013/08/06 05:15, Dave Mischler wrote:
> I have an i5-2500 machine 8GB RAM now running 9.2-RC1 amd64 with the
> GENERIC kernel. Today, while still running 9.2-BETA2, I updated my
> source tree and started building world with idprio 31 and I looked back
> a while later and all the CPU cores and disk were essentially idle, and
> hardly any progress had been made on the build. I stopped and restarted
> the build without the idle priority setting and it ran fine. Anybody
> else seen any of this? Anybody know about any fairly recent changes that
> might account for it?
>
> I did a "rm -rf /usr/src /usr/obj" and loaded a new source tree before
> going to RC1.  I still see odd behavior at RC1.  Sometimes it works just
> like it should (i.e. compute bound processes use most/all of the
> available CPU time), but a lot of the time both the CPU and disk are
> idle (e.g. CPU 97.8% idle, disk 1% busy per systat).  I don't think I
> ever saw this behavior before while running "make buildworld -j4".  Can
> anyone else confirm/rebut my findings?  Thanks.
>
>

idle should never be used, it can cause long term priority inversion
in kernel, make the system slower.